Studies on Extracts of Some Medicinal Plants Traditionally Used for Dermatological Disorders in Ethiopia

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Date

2004-02

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Addis Ababa University

Abstract

Key words: traditional medicine, medicinal plants, antimicrobial activities, anti-inflammatory test, skin sensitization test, topical formulations. The majority of the populations in the developing world rely on traditional medicine for their primary healthcare needs. Herbal therapy predominates in traditional medical practices as well as in complimentary/alternative medicine practiced in the developed world. Among the indications where traditional herbal medicines are used, skin and skin related disorders, which also happen to be common diseases in the communities, rank among the top. This study had the objective of evaluating the extracts of four medicinal plants traditionally used for skin diseases, namely Inula confertiflora, Clematis simensis, Zehneria scabra and Pycnostachys abyssinica, for some of their claimed activities by both in vitro and in vivo methods. The 80 % methanol extract of the dried, ground plant materials was prepared. The plant extracts were then tested for antimicrobial activity against common bacterial and fungal pathogens by the agar well diffusion method. Furthermore, the 80% methanol extract of I. confertiflora was subjected to minimum inhibitory concentration (MIC) determination, in vivo studies such as antiinflammatory and skin sensitization tests as well as in vitro tests such as preliminary screening for the presence of some plant constituents, TLC analysis, and evaluation of topical antimicrobial formulations of the plant extracts. The results of the study indicated all of the plant extracts to exhibit antimicrobial activities against one of the most common bacterial pathogens, namely Staphylococcus aureus (ATCC). x Although these activities were not impressive especially as compared to the positive control used, they lend some credibility to the traditional uses of the plants. Good antifungal activity was demonstrated by one of the plant extracts (I. confertiflora) against Trichophyton mentagrophytes, which was further corroborated by the agar dilution method. I. confertiflora (80% methanol) extract proved to exert a good anti-inflammatory activity at a dose of 1000 mg/kg but not at a lower dose (500 mg/ml) in the carrageenan-induced paw edema test. These activities support the traditional use of this plant. Furthermore, the 80% methanol extract of I. confertiflora, was not found to be a skin sensitizer in the mouse ear swelling test as opposed to its petroleum ether counterpart, which demonstrated a strong sensitizing property. Some secondary metabolites such as sesquiterpene lactones and flavonoids were detected, which may be responsible for some of the demonstrated pharmacological activities of this plant. Evaluation of topical formulations of the 80% methanol extract of I. confertiflora demonstrated that the hydrophilic formulations exhibited higher antimicrobial activities compared to the lipophilic formulations. The activity of the hydrophilic formulations against T. mentagrophytes was comparable to the commercially available antifungal products tested. These bases could thus be used as a starting point for further formulation studies.

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Keywords

Traditional medicine; medicinal plants; antimicrobial activities; anti-inflammatory test;skin sensitization test;topical formulations

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